Multiple-input multiple-output (MIMO) and multiple-input single-output communications systems (MISO) use beamforming for increasing bandwidth.
WO 2004/038952 A2 describes channel estimation and spatial processing for a wireless time-division duplexed (TDD) MIMO communications system. Exploiting reciprocal channel characteristics simplifies the channel state estimation and spatial processing both at the transmitter and at the receiver side.
US 2007/0177681 A1 relates to a wireless MIMO orthogonal frequency division multiplexing (OFDM) communications system using eigenbeam forming in a downlink transmitter. An uplink feedback device provides short-term and long-term eigenbeam forming vectors to the downlink transmitter. In the downlink transmitter, an eigenmode generator generates an eigenbeam forming vector for each of a plurality of reproduced signals output from a signal reproducer at each subcarrier on the basis of the eigenbeam forming vectors. The use of short-term and long-term eigenbeam forming vectors reduces the amount of feedback information.
EP 2019496 A1 refers to a powerline communications system combining Eigenbeamforming with an adaptive orthogonal frequency division multiplex method, wherein channel state information is fed back from a receiver unit to a transmitter unit.
EP 2061160 A1 describes another powerline communications system precoding both training symbols and payload data without exchange of channel state information between the communications devices.
It is an object of the invention to provide a method and devices for enhancing data throughput in powerline communications systems and to improve interference and coexistence properties in wired communications systems.
The object is achieved by a communications systems according to claim 1, by communications devices adapted for the communications systems as they are claimed in claims 8 and 10 and by a method for operating a communications system as claimed in claim 11. Further embodiments are defined in the dependent claims respectively. Details of the invention will become more apparent from the following description of embodiments in connection with the accompanying drawings, wherein features of the various embodiments may be combined unless they exclude each other.